The present invention is directed to a nail to be driven into hard receiving materials such as concrete, rock, metal and the like with the nail having a shank and a head axially penetrated by the shank. The head has a larger outside diameter than the shank. The material forming the shank is harder than the material forming the head.
Nails of the above type are driven into hard receiving materials such as concrete, rock, metal and the like by explosive powder charge operated setting tools. These nails can be used for attaching parts to the hard receiving material and they can also be driven directly into the hard receiving materials for use as junction elements. Where the nails are used to fasten parts, they usually have a flange-like head. If they are used as junction elements, the head can have a thread or other engagement means such as a transverse bore. If the nails have a thread, they are usually characterized as bolts or studs.
Such nails are required to have a high mechanical strength because of the stresses developed in the driving operation. Due to the type of application, a high resistance to corrosion is also required. These two requirements have not been combined in nails used in the past. A compromise was found by using austenitic steels to provide corrosion resistance and the slightly lower strength of such nails was found to be advantageous for shaping work in fabrication. Because of the uses of these nails, the lower mechanical strength has been disadvantageous.
Known austenitic steels alloyed with nitrogen have a high mechanical strength and also a high resistance to corrosion. Such nails have not been used, because they are very difficult to form or shape. Shapes of the head required for different applications cannot be formed from such steels.
The fabrication of expensive head shapes, such as disclosed in U.S. Pat. No. 2,353,315, cannot be produced from the austenitic steels alloyed with nitrogen. For these complicated and expensive head shapes, a soft material is used according to U.S. Pat. No. 2,353,315 and is connected in a positively locked manner with the shank; however the shank does not have a high mechanical strength. For the nails disclosed in this patent, a material with low mechanical strength is adequate for fabrication of the shank, since the nails are not being driven into hard receiving materials by explosive powder charge operated setting tools. The use of such known nails in explosive powder charge operated setting tools is barred due to economic considerations, since nails for explosive powder charge operated setting tools are formed mostly as mass produced items, whereby the expensive fabricating manner set forth in U.S. Pat. No. 2,353,315 is unsuitable.